1. Field of the Invention
The present invention relates generally to the field of apparatus for binding a book and more particulary, to automatic bookbinding apparatus which utilize a binding tape comprised of a substrate which carries an adhesive.
2. Description of Related Art
Apparatus for binding books utilizing a binding tape carrying heat and/or pressure actuated adhesives are well known. For example, U.S. Pat. Nos. 3,928,119 and 3,911,517 disclose a bookbinding machine for binding a stack of sheets. The stack of sheets to be bound is first positioned on a movable plate and clamped between a pair of guides. A binding tape is positioned under the movable plate, below the spine of the book. The binding tape is supported intermediate two moveable heated platens and above a fixed heated platen.
Once the book is positioned, the moveable plate is moved away from the book and the book is translated downward, towards the binding strip. The spine of the book engages the binding strip and forces the strip down between the two moveable heated platen until the center of the strip contacts the fixed heated platen. The moveable heated platens are positioned apart a distance slightly greater than the width of the book so that the periphery of the binding tape will fold over the front and rear book covers.
The moveable platens are then forced together so as to seal the periphery of the binding strip to the front and back cover sheets using heat and pressure. The fixed heated platen functions to melt the central binding tape adhesive so as to wet the spine of the book (the edges of the sheet) with adhesive. The moveable platens are then retracted and the bound book is removed and permitted to cool.
A further bookbinding apparatus is disclosed in U.S. Pat. No. 3,531,358. The stack of sheets to be bound is gripped between a pair of opposing clamps. A binding tape having heat and pressure sensitive adhesive is positioned on top of a pair of heated moveable platens. The stack is then lowered on the binding tape so that molten adhesive contacts the edges of the sheets.
The pair of opposing platens then separate a distance slightly wider than the stack and the stack is forced down between the opposing platens thereby causing the peripheries of the binding tape to fold up against the front and back covers of the stack. The opposing platens are then forced against the stack so as to seal the tape to the covers. The platens are then opened so that the bound book may be removed.
U.S. Pat. No. 3,911,517 also discloses apparatus for feeding the binding tape into the binding apparatus and for accepting binding tapes of varying widths to accommodate stacks of varying thickness. The thickness of the stack is measured by manual rotation of a calipering knob which causes a pair of tape guides to move with respect to one another so that the guides will accept a tape of appropriate width for the stack to be bound. Since the tape is always centered below the stack to be bound, it is not necessary to justify the tape so the center of the tape is always located at the center of the edge of the stack.
A principal disadvantage of the previously-described prior art tape handling mechanism is that it is required, at least every time a stack which differs in thickness from the previous stack is to be bound, to manually adjust the machine. This presents a serious disadvantage when it is necessary to bind a large mumber of stacks of varying thickness.
The present invention overcomes the disadvantages of the prior art tape handling mechanisms in that the beginning of each binding operation the stack is placed in the machine and the thickness of the stack is automatically measured and a tape guide is automatically adjusted. No intervention by the operator is required. In one embodiment of the invention, apparatus are provided for justifying the tape relative to the stack so that the tape will be centered on the spine of the bound book for all stack thicknesses. These and other advantages of the present invention will become apparent to those skilled in the art upon reading the following Detailed Description of the Preferred Embodiment together with the drawings.